DNA-binding studies of mixed-ligand (ethylenediamine)ruthenium(II) complexes

A series of mixed-ligand ruthenium(II) complexes of the type [Ru(en)(2)bpy](2+) (bpy=2,2-bipyridine; 1), [Ru(en)(2)phen](2+) (phen=1,10-phenantroline; 2), [Ru(en)(2)IP](2+) (IP=imidazo[4,5-f][1,10]phenanthroline; 3), and [Ru(en)(2)PIP](2+) (PIP=2-phenylimidazo[4,5-f][1,10]phenanthroline; 4) have been isolated and characterized by UV/VIS, IR, and (1)H-NMR spectral methods. The binding of the complexes with calf thymus DNA has been investigated by absorption, emission spectroscopy, viscosity measurements, DNA melting, and DNA photo-cleavage. The spectroscopic studies together with viscosity measurements and DNA melting studies support that complexes 1 and 2 bind to CT DNA (=calf thymus DNA) by groove mode. Complex 2 binds more avidly to CT DNA than complex 1, complexes 3 and 4 bind to CT DNA by intercalation mode, 4 binds more avidly to CT DNA than 3. Noticeably, the four complexes have been found to be efficient photosensitisers for strand scissions in plasmid DNA.     

Syntheses and DNA-binding studies of two ruthenium(II) complexes containing one ancillary ligand of bpy or phen: [Ru(bpy)(pp[2,3]p)2](ClO4)2 and [Ru(phen)(pp[2,3]p)2](ClO4)2

Two new ruthenium(II) complexes of [Ru(bpy)(pp[2,3]p)2](ClO4)2 and [Ru(phen)(pp[2,3]p)2](ClO4)(2) (bpy=2,2'-bipyridine, phen=1,10-phenanthroline, pp[2,3]p=pyrido[2',3':5,6]pyrazino[2,3-f][1,10]phenanthroline) have been synthesized and characterized by elemental analysis and 1H NMR spectra. The calf thymus DNA-binding properties of the two complexes were investigated by UV-visible and emission spectroscopy, competitive binding experiments with ethidium bromide and viscosity measurements. The results indicate that the two complexes intercalate between the base pairs of the DNA tightly with intrinsic DNA-binding constants of 3.08 x 10(6) and 6.53 x 10(6) M(-1) in buffered 50 mM NaCl, respectively, which are much larger than 6.9 x 10(5) M(-1) for [Ru(bpy)2(pp[2,3]p)](ClO4)2 containing two ancillary ligands of bpy.     

Synthesis, DNA-binding and photocleavage studies of ruthenium(II) complex with 2-(3'-phenoxyphenyl)imidazo[4,5-f][1,10]phenanthroline

A new polypyridyl ligand MPPIP {MPPIP=2-(3'-phenoxyphenyl)imidazo[4,5-f]-[1,10]phenanthroline} and its ruthenium(II) complexes, [Ru(bpy)(2)MPPIP](2+) (1) (bpy=2,2'-bipyridine) and [Ru(phen)(2)MPPIP](2+) (2) (phen=1,10-phenanthroline) have been synthesized and characterized. The binding of the two complexes to calf thymus DNA (CT-DNA) has been investigated with spectrophotometric methods, viscosity measurements, as well as equilibrium dialysis and circular dichroism spectroscopy. The results suggest that both complexes bind to CT-DNA through intercalation, and enantioselectively interact with CT-DNA in a way. However, complex 2 is a much better candidate as an enantioselective binder to CT-DNA than complex 1. When irradiated at 365nm, both complexes have also been found to promote the photocleavage of plasmid pBR322 DNA.     

Photoelectron transfer processes with ruthenium(II) polypyridyl complexes and Cu/Zn superoxide dismutase

The processes that are photoinduced by [Ru(bpz)(3)](2+) (bpz = 2,2'-bipyrazyl) in the presence of Cu/Zn superoxide dismutase (Cu/Zn SOD) are investigated by laser flash photolysis and electron paramagnetic resonance (EPR) spectroscopy; they are compared to those of the system [Ru(bpy)(3)(2+)-Cu/Zn SOD]. Although the mechanism is complicated, primary and secondary reactions can be evidenced. First, the excited [Ru(bpz)(3)](2+) complex is quenched reductively by Cu/Zn SOD with the production of a reduced complex and an oxidized enzyme. The oxidation site of Cu/Zn SOD is proposed to correspond to amino acids located on the surface of the protein. Afterward and only when this reductive electron transfer to the excited complex has produced enough oxidized protein, another electron-transfer process can be evidenced. In this case, however, the charge-transfer process takes place in the other direction, i.e., from the excited complex to the Cu(II) center of the SOD with the formation of Ru(III) and Cu(I) species. This proposed mechanism is supported by the fact that [Ru(bpy)(3)](2+), which is less photo-oxidizing than [Ru(bpz)(3)](2+), exhibits no photoreaction with Cu/Zn SOD. Because Ru(III) species are generated as intermediates with [Ru(bpz)(3)](2+), they are proposed to be responsible for the enhancement of [poly(dG-dC)](2) and [poly(dA-dT)](2) oxidation observed when Cu/Zn SOD is added to the [Ru(bpz)(3)](2+)-DNA system.     

Mixing ratio-dependent energy transfer from DNA-bound 4',6-diamidino-2-phenylindole to [Ru(1,10-phenanthroline)(2)dipyrido[3,2-a:2',3'-c]phenazine](2+)

The binding mode of Delta- and Lambda-[Ru(1,10-phenanthroline)(2)dipyrido[3,2-a:2',3'-c]phenazine](2+) ([Ru(phen)(2)DPPZ](2+)) to DNA in the presence of 4',6-diamidino-2-phenylindole (DAPI) at a low and high [DAPI]/[DNA base] ratio (0.02 and 0.20, respectively) was investigated using electric absorption and circular dichroism spectroscopy. The spectral properties of both the Delta- and Lambda-[Ru(phen)(2)DPPZ](2+) were not altered in the presence of DAPI disregarding the [DAPI]/[DNA] ratio, suggesting that the presence of DAPI in the minor groove of DNA does not affect the binding mode of the [Ru(phen)(2)DPPZ](2+) complex to DNA. The transferring excited energy of DAPI to both Delta- and Lambda-[Ru(phen)(2)DPPZ](2+) occurs through F?rster type resonance when they both spontaneously bound to DNA. At a high [DAPI]/[DNA] ratios, an upward bending curve in the Stern-Volmer plot, and a shortening the DAPI fluorescence decay time with increasing [Ru(phen)(2)DPPZ](2+) concentration were found. These results indicate that the quenching of the DAPI's fluorescence occurs through both the static and dynamic mechanisms. In contrast, the quenching mechanism at a low [DAPI]/[DNA] ratios was found to be purely static. The static quenching constant decreased linearly with respect to the [DAPI]/[DNA] ratio. Decrease in quenching efficiency can be explained by the association constant of [Ru(phen)(2)DPPZ](2+) to DNA while being within a quenchable distance from a DAPI molecule.     

Picosecond Kerr-gated time-resolved resonance Raman spectroscopy of the [Ru(phen)(2)dppz](2+) interaction with DNA

To investigate the basis of the 'light-switch' effect, the solvent dependence of the Kerr-gated picosecond-time resolved resonance Raman (TR(3)) spectra of [Ru(bpy)(2)dppz](2+), [Ru(phen)(2)dppz](2+), and the modified complex [Ru(phen)(2)cpdppzOMe](2+) and a dimer [mu-C4(cpdppz)(2)-(phen)(4)Ru(2)](4+) were studied. The investigation focussed on comparing the behaviour of [Ru(phen)(2)dppz](2+) in acetonitrile, ethanol, H(2)O, D(2)O, and DNA. The data are consistent with a model wherein excitation induces metal-to-ligand charge transfer (MLCT) to any of the ligands (termed the 'precursor' state) which, by interligand electron transfer (ILET), produces an excited state localised on the dppz ligand, MLCT(1). In water this state relaxes with a characteristic time of approximately 6 ps to a non-emissive state (MLCT(2)). The TR(3) spectra in water, acetonitrile and DNA are all distinctly different. However, the early (4 ps) water spectrum resembles the spectrum in DNA. This interesting observation suggests that the DNA-bound excited state of the complex can be thought of as a model for the initial, poorly solvated state in water.     

One-step electrochemically co-assembled redox-active [Ru(bpy)(2)(tatp)](2+)-BSA-SWCNTs hybrid film for non-redox protein biosensors

A redox-active [Ru(bpy)(2)(tatp)](2+)-BSA-SWCNTs (bpy=2,2'-bipyridine, tatp=1,4,8,9-tetra-aza-triphenylene, BSA=bovine serum albumin, SWCNTs=single-walled carbon nanotubes) hybrid film is fabricated on an indium-tin oxide (ITO) electrode via one-step electrochemical co-assembly approach. BSA is inherently dispersive and therefore served as the linking mediator of SWCNTs, which facilitate the redox reactions of [Ru(bpy)(2)(tatp)](2+) employed as a reporter of BSA. The evidences from differential pulse voltammetry, cyclic voltammetry, scanning electron microscope, emission spectroscopy and fluorescence microscope reveal that the [Ru(bpy)(2)(tatp)](2+)-BSA-SWCNTs hybrid can be electrochemically co-assembled on the ITO electrode, showing two pairs of well-defined Ru(II)-based redox waves. Furthermore, the electrochemical co-assembly of the [Ru(bpy)(2)(tatp)](2+)-BSA-SWCNTs hybrid is found to be strongly dependent on the simultaneous presence of BSA and SWCNTs, indicating a good linear response to BSA in the range from 6 to 50mgL(-1). The results from this study provide an electrochemical co-assembly method for the development of non-redox protein biosensors.     

The dichotomy in the DNA-binding behaviour of ruthenium(II) complexes bearing benzoxazole and benzothiazole groups

The substituted tris(bipyridine)ruthenium(II) complexes {[Ru(bpy)(2)(4,4'-bbob)](2+) and [Ru(bpy)(2)(5,5'-bbob)](2+) [where bpy=2,2'-bipyridine and bbob=bis(benzoxazol-2-yl)-2,2'-bipyridine] have been prepared and compared to the previously studied complex [Ru(bpy)(2)(4,4'-bbtb)](2+) [where bbtb=bis(benzothiazol-2-yl)-2,2'-bipyridine]. From the UV/VIS titration studies, Delta-[Ru(bpy)(2)(4,4'-bbob)](2+) displays a stronger association than the Lambda-isomer with calf-thymus DNA (ct-DNA). For [Ru(bpy)(2)(5,5'-bbob)](2+), there appears to be minimal interaction with ct-DNA. The results of fluorescence titration studies suggest that [Ru(bpy)(2)(4,4'-bbob)](2+) gives an increase in emission intensity with increasing ct-DNA concentrations, with an enantiopreference for the Delta isomer, confirmed by membrane dialysis studies. The fluorescent intercalation displacement studies revealed that [Ru(bpy)(2)(4,4'-bbob)](2+) and [Ru(bpy)(2)(5,5'-bbob)](2+) display a preference for more open DNA structures such as bulge and hairpin sequences. While Lambda-[Ru(bpy)(2)(4,4'-bbtb)](2+) has shown the most significant affinity for all the oligonucleotides sequences screened in previous studies, it is the Delta isomer of the comparable benzoxazole ruthenium(II) complex (Delta-[Ru(bpy)(2)(4,4'-bbob)](2+)) that preferentially binds to DNA.     

Interaction of polypyridyl ruthenium (II) complex containing asymmetric ligand with DNA

A novel asymmetric bidentate ruthenium (II) complex, [Ru(bpy)(2)(PYNI)](2+) (bpy=2,2'-bipyridine, PYNI=2-(2'-pyridyl)naphthoimidazole), has been synthesized and characterized by elemental analysis, ES-MS (electrospray mass spectra) and (1)H NMR. The electrochemical behaviors of this complex were studied by cyclic voltammetry. DNA interaction studies suggest that [Ru(bpy)(2)(PYNI)](2+) binds to calf thymus DNA (CT-DNA) in an intercalative mode. Interestingly, this new Ru(II) complex has also been found to promote cleavage of plasmid pBR 322 DNA from the supercoiled form I to the open circular form II upon irradiation.     

The light switch effect upon the association of [Ru(1,10-phenanthroline)2dipyrido[3,2-a:2',3'-c]phenazine]2+ with single stranded poly(dA) and poly(dT)

Large enhancement in the luminescence intensity of the Delta- and Lambda-Ru(phenanthroline)(2)dipyrido[3,2-a:2',3'-c]phenazine](2+) ([Ru(phen)(2)DPPZ](2+)) complexes upon their association with single stranded poly(dA) and poly(dT) is reported in this work. As the mixing ratio ([[Ru(phen)(2)DPPZ](2+)]/[DNA base]) increases, the luminescence intensity increase in a sigmoidal manner, indicating that the enhancement involves some cooperativity. At a high mixing ratio, the luminescence properties are affected by the nature of the DNA bases and not by the absolute configuration of the [Ru(phen)(2)DPPZ](2+) complex, indicating that the single stranded poly(dA) and poly(dT) do not recognize the configuration of the metal complex. In the case of the Lambda-[Ru(phen)(2)DPPZ](2+)-poly(dT) complex, the manner of the enhancement is somewhat different from the other Ru(II) complex-polynucelotide combinations: the luminescence intensity reached a maximum at an intermediate mixing ratio of 0.32, and gradually decreased as the mixing ratio increased. In contrast to other complexes at high mixing ratios, an upward bending curve was found in the Stern-Volmer plot, which indicates that the micro-environment of the Lambda-[Ru(phen)(2)DPPZ](2+) is heterogeneous. In the Delta-[Ru(phen)(2)DPPZ](2+)-poly(dT) complex case, formation of this highly luminescent species at an intermediate mixing ratio is far less effective.     

Electrochemiluminescence of dipicolinic acid (DPA) and (bpy)(2)Ru(DPA)(+) (bpy = 2,2'-bipyridine).

The spectroscopic and electrochemiluminescence (ECL) properties of dipicolinic acid (DPA), (bpy)(2)Ru(2+) (bpy = 2,2'-bipyridine) and the species formed when DPA and (bpy)(2)Ru(2+) [abbreviated to (bpy)(2)Ru(DPA)(+)] are allowed to react are reported. The UV-Vis absorption maxima for (bpy)(2)Ru(2+) and (bpy)(2)Ru(DPA)(+) are 493 and 475 nm, respectively, indicating the in situ formation of a complex between DPA and (bpy)(2)Ru(2+). DPA, (bpy)(2)Ru(2+) and (bpy)(2)Ru(DPA)(+) display ECL upon oxidation in the presence of the oxidative-reductive co-reactant tri-n-propylamine (TPrA). The ECL of (bpy)(2)Ru(DPA)(+) is at least two-fold higher than either of the parent species. An ECL spectrum of (bpy)(2)Ru(DPA)(+) displays a peak maximum 40 nm red-shifted from the photoluminescence peak maximum, suggesting that the excited state formed electrochemically is different from that formed spectroscopically.     

Synthesis, characterization, DNA-binding and photocleavage studies of [Ru(bpy)2(PPIP)]2+ and [Ru(phen)2(PPIP)]2+

A novel ligand 2-(4'-phenoxy-phenyl)imidazo[4,5-f][1,10]phenanthroline (PPIP) and its complexes [Ru(bpy)(2)(PPIP)](2+) (1) (bpy = 2,2'-bipyridine) and [Ru(phen)(2)(PPIP)](2+) (2) (phen = 1,10-phenanthroline) have been synthesized and characterized by mass spectroscopy, (1)H NMR and cyclic voltammetry. The interaction of two complexes with calf thymus DNA (CT-DNA) was investigated by spectroscopic and viscosity measurements. The results suggest that both complexes bind to DNA via an intercalative mode. Both complexes have also been found to promote the photocleavage of plasmid pBR 322 DNA under irradiated.     

Synthesis, characterization, and DNA-binding of chiral complexes delta- and lambda-[Ru(bpy)2(pyip)]2+

New chiral Ru(II) complexes delta and lambda-[Ru(bpy)(2)(pyip)](PF(6))(2) [(bpy = 2,2'-bipyridine; pyip = (2-(1-pyrenyl)-1H-imidazo[4,5-f] [1,10]phenanthroline] were synthesized and characterized by elemental analysis, (1)H NMR, ESI-MS, IR, and CD spectra. Their DNA-binding properties were studied by means of UV-vis, emission spectra, CD spectra and viscosity measurements. A subtle but detectable difference was observed in the interaction of both enantiomer with CT-DNA. Spectroscopy experiments indicated that each of these complexes could interact with the DNA. The DNA-binding of the Delta-enantiomer was stronger than that of Lambda-enantiomer. DNA-viscosity experiments provided evidence that both Delta- and Lambda-[Ru(bpy)(2)(pyip)](PF(6))(2) bound to DNA by intercalation. At the same time, the DNA-photocleavage properties of the complexes were investigated too. Under irradiation with UV light, Ru(II) complexes showed different efficiency of cleaving DNA.     

DNA binding by Ru(II)–bis(bipyridine)–pteridinyl complexes

The interactions of five bis(bipyridyl) Ru(II) complexes of pteridinyl-phenanthroline ligands with calf thymus DNA have been studied. The pteridinyl extensions were selected to provide hydrogen-bonding patterns complementary to the purine and pyrimidine bases of DNA and RNA. The study includes three new complexes [Ru(bpy)(2)(L-pterin)](2+), [Ru(bpy)(2)(L-amino)](2+), and [Ru(bpy)(2)(L-diamino)](2+) (bpy is 2,2'-bipyridine and L-pterin, L-amino, and L-diamino are phenanthroline fused to pterin, 4-aminopteridine, and 2,4-diaminopteridine), two previously reported complexes [Ru(bpy)(2)(L-allox)](2+) and [Ru(bpy)(2)(L-Me(2)allox)](2+) (L-allox and L-Me(2)allox are phenanthroline fused to alloxazine and 1,3-dimethyalloxazine), the well-known DNA intercalator [Ru(bpy)(2)(dppz)](2+) (dppz is dipyridophenazine), and the negative control [Ru(bpy)(3)](2+). Reported are the syntheses of the three new Ru-pteridinyl complexes and the results of calf thymus DNA binding experiments as probed by absorption and fluorescence spectroscopy, viscometry, and thermal denaturation titrations. All Ru-pteridine complexes bind to DNA via an intercalative mode of comparable strength. Two of these four complexes-[Ru(bpy)(2)(L-pterin)](2+) and [Ru(bpy)(2)(L-allox)](2+)-exhibit biphasic DNA melting curves interpreted as reflecting exceptionally stable surface binding. Three new complexes-[Ru(bpy)(2)(L-diamino)](2+), [Ru(bpy)(2)(L-amino)](2) and [Ru(bpy)(2)(L-pterin)](2+)-behave as DNA molecular "light switches."     

The effects of grafting of 2-pyridyl to [Ru(bpy)(2)(Hpip)](2+) on acid-base and DNA-binding properties: experimental and DFT studies

A new Ru(II) complex of [Ru(bpy)(2)(Hpip)](2+) {bpy = 2,2'bipyridine; Hppip = 2-(4-(pyridin-2-yl)phenyl)-1H-imidazo[4,5-f][1,10]phenanthroline} has been synthesized by grafting of 2-pyridyl to parent complex [Ru(bpy)(2)(Hpip)](2+) {Hppip = 2-(4-phenyl)-1H-imidazo[4,5-f][1,10]phenanthroline}. The acid-base properties of [Ru(bpy)(2)(Hpip)](2+) studied by UV-visible and luminescence spectrophotometric pH titrations, revealed off-on-off luminescence switching of [Ru(bpy)(2)(Hpip)](2+) that was driven by the protonation/deprotonation of the imidazolyl and the pyridyl moieties. The complex was demonstrated to be a DNA intercalator with an intrinsic DNA binding constant of (5.56 ± 0.2) x 10(5) M-1 in buffered 50 mM NaCl, as evidenced by UV-visible and luminescence titrations, reverse salt effect, DNA competitive binding with ethidium bromide, steady-state emission quenching by [Fe(CN)6]4-, DNA melting experiments and viscosity measurements. The density functional theory method was also used to calculate geometric/electronic structures of the complex in an effort to understand the DNA binding properties. All the studies indicated that the introduction of 2-pyridyl onto Hpip ligand is more favorable for extension of conjugate plane of the main ligand than that of phenyl, and for greatly enhanced ct-DNA binding affinity accordingly.     

Synthesis, characterization, DNA-binding and cleavage studies of [Ru(bpy)2(actatp)]2+ and [Ru(phen)2(actatp)]2+ (actatp=acenaphthereno[1,2-b]-1,4,8,9-tetraazariphenylence)

New ligand acenaphthereno[1,2-b]-1,4,8,9-tetraazariphenylence (actatp) and its complexes [Ru(bpy)(2)(actatp)](ClO(4))(2).2H(2)O (1) (bpy=2,2'-bipyridine) and [Ru(phen)(2)(actatp)](ClO(4))(2).2H(2)O (2) (phen=1,10-phenanthroline) have been synthesized and characterized by UV-vis, 1H NMR, and mass spectra. The electrochemical behavior of the two complexes was studied by cyclic voltammetry. The interaction of the two complexes with calf thymus DNA has been investigated by spectrophotometric methods and viscosity measurements. The experimental results suggest that both complexes bind to DNA through an intercalative mode. The circular dichroism signals of the dialysates of the racemic complexes against calf thymus DNA are discussed. When irradiated at 302 nm, both complexes have also been found to promote the photocleavage of plasmid pBR 322 DNA.     

Nucleic acid binding behaviors and cytotoxic properties of a Ru(II) complex

The interactions of complex [Ru(bpy)(2)(hnip)](2+) (1) {bpy?=?2,2'-bipyridine, hnip?=?2-(2-hydroxy-1-naphthyl)imidazo[4,5-f][1,10]phenanthroline} with calf thymus DNA and yeast tRNA were investigated by UV-vis spectroscopy, fluorescence spectroscopy, viscosity, equilibrium dialysis, and circular dichroism. In addition, the antitumor activities of complex 1 were evaluated with MTT method. These results indicate that the structures of DNA and RNA have significant effects on the binding behaviors of complex 1. Further, complex 1 demonstrates different antitumor activities against selected cancer cell lines in vitro.     

Interaction of Lambda- and Delta-[Ru(bpy)2(pbmz)](PF6)2 with the oligonucleotide duplex d(CGCGAATTCGCG)2

The interaction of the enantiomeric complexes Lambda- and Delta-[Ru(bpy)(2)(pbmz)](PF(6))(2) (bpy=2,2'-bipyridine, pbmz=2-(2'-pyridyl)benzimidazole) with the DNA duplex d(CGCGAATTCGCG)(2) was investigated by means of 2D NMR techniques. The synthesis of the enantiomers was based on the optically pure complexes Lambda- and Delta-[Ru(bpy)(2)(py)(2)](2+) and were characterized by CD and NMR spectroscopy. NMR data indicate that both enantiomers bind weakly to the oligonucleotide, approaching from the minor groove at the centre of the helix. The perturbation of the B-DNA conformation is minor with an apparent absence of enantioselectivity. Molecular modelling calculations in conjunction with the NOE data support the suggestion that more than one binding modes are present. The imidazole amine group of the pbmz ligand is probably hydrogen bonded to the DNA phosphodiesteric backbone at the AATT step, and this may provide an explanation for the diminished enantioselectivity observed.     

Ruthenium(II) mixed-ligand complex containing 2-(4'-benzyloxy-phenyl)imidazo[4,5-f][1,10]phenanthroline: synthesis, DNA-binding and photocleavage studies

A novel polypyridyl ligand 2-(4'-benzyloxyphenyl)imidazo[4,5-f][1,10]phenanthroline (BPIP) and its complex [Ru(bpy)2(BPIP)]2+ (1) (bpy=2,2'-bipyridine) and (2) [Ru(phen)2(BPIP)]2+) (phen=1,10-phenanthroline) have been synthesized and characterized by elemental analysis, electrospray mass spectra and 1H NMR. The DNA-binding properties of the two complexes were investigated by spectroscopic and viscosity measurements. The results suggest that both complexes bind to DNA via an intercalative mode. Both complexes can enantioselectively interact with calf thymus DNA (CT-DNA) in a way. The Lambda enantiomer of complex 1 is slightly predominant for binding to CT-DNA to the Delta enantiomer. Under irradiation at 365 nm, both complexes have also been found to promote the photocleavage of plasmid pBR 322 DNA. Inhibitors studies suggest that singlet oxygen ((1)O2) and hydroxyl radical (*OH) play a significant role in the cleavage mechanism for both complexes. Moreover, the DNA-binding and photocleavage properties of both complexes were compared with that of [Ru(bpy)2(BPIP)]2+ and [Ru(phen)2(BPIP)]2+. The experimental results indicate that methene group existence or not have a significant effect on the DNA-binding and cleavage mechanism of these complexes.     

Synthesis and characterization of polypyridineruthenium(II) complexes containing a linear ambidentate ligand, NCO or NCS, and reaction of isocyanato complexes under acidic conditions

Isocyanato and isothiocyanatopolypyridineruthenium complexes, [Ru(NCX)Y(bpy)(py)₂]ⁿ⁺ (bpy=2,2′-bipyridine, PY=pyridine; X=O, Y=NO₂ for n=0, and Y=py for n=1; X=S, Y=NO₂ for n=0, Y=NO for n=2, and Y=py for n=1), were synthesized by the reaction of polypyridineruthenium complexes with potassium cyanate or sodium thiocyanate salt. Isocyanatoruthenium(II) complexes, [Ru(NCO)(NO₂)(bpy)(py)₂] and [Ru(NCO)(bpy)(py)₃]⁺, react under acidic conditions to form the corresponding ammineruthenium complexes, [Ru(NO)(NH₃)(bpy)(py)₂]³⁺. The molecular structures of [Ru(NCO)(bpy)(py)₃]ClO₄, [Ru(NCS)(NO)(bpy)(py)₂](PF₆)₂ and [Ru(NO)(NH₃)(bpy)(py)₂](PF₆)₃ were determined by X-ray crystallography.